Johannes Zellner1,2, Brian Johnstone3, Frank Barry4, Henning Madry5,6. 1. Department of Traumatology, Caritas Hospital St. Josef, Regensburg, Germany. 2. Laboratory for Experimental Trauma Surgery, Department of Trauma Surgery, University Medical Centre Regensburg, Germany. 3. Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, Portland, Oregon, USA. 4. Regenerative Medicine Institute, National University of Ireland Galway, Ireland. 5. Center of Experimental Orthopaedics, Saarland University Medical Center and Saarland University, Homburg, Saar, Germany. 6. Department of Orthopaedic Surgery, Saarland University Medical Center and Saarland University, Homburg, Saar, Germany.